Multiple display electronic caliper

ABSTRACT

In addition to other aspects disclosed, a caliper is configured to measure at least one physical dimension. The caliper has a display configured to present a first representation and a second representation of a measurement provided by the caliper. The format of the first representation is different from the format of the second representation, and the first representation is approximately simultaneously displayed with the second representation.

CLAIM OF PRIORITY

This application is a continuation application and claims priority under35 U.S.C. §120 to U.S. patent application Ser. No. 12/848,376 filed onAug. 2, 2010 now U.S. Pat. No. 8,037,616 issued on Oct. 18, 2011, whichis a continuation application and claims priority under 35 U.S.C. §120to U.S. patent application Ser. No. 11/969,832 filed on Jan. 4, 2008 nowU.S. Pat. No. 7,765,712 issued on Aug. 3, 2010, which claims benefitunder U.S.C. §119(e) to U.S. Provisional Application Ser. No.60/883,687, filed on Jan. 5, 2007, the entire contents of which arehereby incorporated by reference.

TECHNICAL FIELD

This invention relates to an electronic caliper that presentsinformation with multiple displays.

BACKGROUND

In conventional length measuring mechanical instruments, a vernier scaleor a dial indicator is used to measure one or more dimensions. Theseconventional length measuring instruments present a possibility ofmisreading the instrument due to reading errors and user error (e.g.,due to the eyesight of the user).

With the progression in the art of digital displays in various fields,digital displays have been progressively applied to various types ofmeasuring instruments. Caliper devices are not an exception and thereexists calipers with a digital display. However, a single display mayonly conveniently provide a single piece of information that may lead toinefficient use of the caliper device and may be another source of usererror.

SUMMARY

In general, in some aspects of the disclosure, an apparatus includes acaliper configured to measure at least one physical dimension. Thecaliper has a display configured to present a first representation and asecond representation of a measurement provided by the caliper. Theformat of the first representation is different from the format of thesecond representation, and the first representation is approximatelysimultaneously displayed with the second representation.

The format of the first representation may include a decimal format, afractional format, etc. The format of the second representation mayinclude a decimal format, a fractional format etc. and be different fromthe format of the first representation. The first format may have metricunits and the second format may have U.S. units. The resolution of thefirst representation may be selectable. The format of the firstrepresentation may include a first measurement unit and the format ofthe second representation may include a second measurement unit,different from the first measurement unit. The apparatus may include anelectronics package that includes a display. The display may include aunit indicator and a variance indicator. The electronics package may beconfigured to provide data representative of the first representationand the second representation to an external display module. A hardwireor wireless connection may be used to provide the data from theelectronics package to the external display module.

In some aspects of the disclosure, a method is disclosed thatsimultaneously displays on a display of a caliper, a firstrepresentation and a second representation of a measurement provided bythe caliper. The format of the first representation is different fromthe format of the second representation.

The caliper may provide data that represents the first representationand the second representation to an external display module. The formatof the first representation may include one of a decimal format and afractional format. The first format may have metric units and the secondformat may have U.S. units.

In some aspects of the disclosure, a computer program product encoded ona computer-readable medium is operable to cause a data processingapparatus to perform operations that include simultaneously displayingon a display of a caliper a first representation and a secondrepresentation of a measurement provided by the caliper. The format ofthe first representation is different from the format of the secondrepresentation.

The computer program product may be further operable to cause the dataprocessing apparatus to perform operations that include providing datathat represents the first representation and the second representationto an external display module. The format of the first representationmay include a decimal format, a fractional format, etc. The first formatmay have metric units and the second format may have U.S. units.

DESCRIPTION OF DRAWINGS

FIGS. 1 and 2 illustrate exemplary calipers.

FIGS. 3 and 4 illustrate exemplary displays.

FIGS. 5 and 6 as flowcharts of operations of a display.

DETAILED DESCRIPTION

FIG. 1 illustrates and example of an electronic caliper 100 that iscapable of presenting information on two or more displays. For example,information representative of a caliper measurement may besimultaneously presented on the two or more displays. One or moretechniques may be incorporated into the caliper 100 to provide ameasurement. For example, the caliper 100 may include a main scale andan auxiliary scale whose relative movement to each other provides ameasurement. In another implementation (referred to as a magnescale), asignal, which is produced due to the movement of scales relative to amagnetic tape, provides a measure of a dimension. In still anotherimplementation, a caliper device may include an encoder that allowslight to be directed toward an optical measuring device. A dimensionalmeasurement is provided through a series of reflections based upon thecaliper being placed in a measurement position.

In this particular implementation, the caliper 100 is capable ofmeasuring the outside dimensions of objects using a set of outside jaws105. Caliper 100 is also capable of measuring the inside dimensions ofobjects using a set of inside jaws 115. The caliper 100 also has a depthgauge 120 for measuring the depth of an object.

For producing a measurement, the caliper 100 includes an electronicspackage 125. The electronics package 125 is attached to the caliper 100and performs functions associated with measurements along with otherfunctions such as numerical calculations, preparing data for display,interfacing with other portions of the caliper 100, etc. The electronicspackage 125 has a display 126, which is capable of presenting at leasttwo pieces of information that may be related or unrelated. For example,the display 126 may present two different representations of themeasurement. In this illustration, the display 126 presents a decimalrepresentation 130 of the current measurement in decimal form and afractional representation 135 of the measurement in fractional form. Thedisplay 126 also displays, for example, a units indicator 140 that iscapable of indicating the measurement units currently in use (e.g.,inches, millimeters, etc.). The representation 130 and therepresentation 135 may be dedicated to the display of decimal orfractional numerical formats, or they may display either decimal and/orfractional formats interchangeably. In some embodiments, the display 126may also be capable of presenting other types of representations inaddition to those already described. These additional representationsmay be used to provide the user with a simultaneous display of, forexample, a single measurement in inches in decimal form, inches infractional form, millimeters in decimal form, etc.

In some embodiments, the display 126 may have additional unitsindicators similar to units indicator 140, in which each displayedrepresentation may have an associated units indicator. For example, thedisplay 126 may show a single measurement in two or more simultaneousrepresentations, where each representation may be shown using differentunits of measurement (e.g., showing 1.00 inches and 25.4 millimeters)along with their respective units indicators.

The electronics package 125 may also include a group of buttons 145 (orother type of user interface) that may be used to control variousoperations and aspects of the caliper 100. These operations may include,for example, powering on or off the caliper's 100 electronics, selectingU.S. or metric units, selecting display configurations, selecting adecimal or fractional representation, resetting (“zeroing”) themeasurement, activating a backlight, etc.

In this implementation, the electronics package 125 includes a displaycontroller 170, which may perform various computational tasks associatedwith the operation of the caliper 100. The display controller 170 mayinclude components such as a processor 175, and a memory 180. Theprocessor 175 may be implemented as one or more general purposeprocessors or processors customized for particular functions andoperations. The memory 180 may be implemented, for example, in volatileor non-volatile memory (e.g., read-only memory (ROM), random accessmemory (RAM), dynamic RAM (DRAM), static RAM (SRAM)), etc. A userinterface controller 190 may be included for collecting information andprovide information for output (e.g., presentation on the display 126).For example, the user interface controller 190 may receive data from thecollection of buttons 145 in order to provide the processor 175 withuser input information, which may be used, for example, to modify theprocessor 175 operations. The user interface controller 190 may alsoindividually, or in combination with the processor 175, assist withdriving the display 126. The memory 180 may contain instructions,applications, data structures, data files or other types of informationthat may be used by the processor 175 and/or the user interfacecontroller 190 to execute operations. In this implementation the memory180 includes a display driver 185 that is executed by the processor 175to control the presentation of information on the display 126. Thedisplay driver 185 may also assist in other operations such as readingmeasurement data and formatting the data for presentation on the display126.

FIG. 2 illustrates another exemplary electronic caliper 200 that iscapable of simultaneously displaying two representations of ameasurement. In this example, the caliper 200 comprises an electronicspackage 205 that is absent an onboard display. In this implementation,an external display module 210 is capable of displaying measurementinformation and user interactivity information. The display module 210includes a display 215 and a collection of buttons 220. In this example,the external display module 210 also includes the display controller 170that controls the presentation of information on the display 215 (alongwith other functions). In this implementation, the display controller170, the collection of buttons 220 and the display 215 are locatedseparate from the electronics package 205. However, in otherimplementations, one or more of the components may be included in theelectronics package 205. The display 215 is capable of simultaneouslypresenting measurement information in multiple representations. In thisillustration, the display 215 is simultaneously presenting a singlemeasurement in both a decimal representation 230 and a fractionalrepresentation 235 along with a units indication 240. One or both of therepresentation 230 and the representation 235 may be dedicated to thedisplay of decimal or fractional numerical formats, or they may displayeither decimal and/or fractional formats interchangeably. The unitsindication 240 presents the units of measurement that correlates to bothrepresentations 230 and 235, however, in some arrangements, eachrepresentation may be associated with one or more dedicated unitsindicators.

The electronics package 205 and the external display module 210 arelinked by a electrical connection 250. The connection 250 is used tocommunicate electronic data and commands between the electronics package205 and the external display module 210. For example, data representingone or more measurements performed by the caliper 200 may be sent viathe electrical connection 250 to the external display module 210. Theelectrical connection 250 may include one or more communicationtechniques. For example, one or more hardwire connections (e.g., serialcable, parallel cable, etc.) may be implemented. Wireless techniques mayalso be used such as infrared (IR), radio frequency (RF), Bluetooth,ZigBee, wireless Ethernet, or other electromagnetic linking techniques.One or more protocols, transmission standards, and data formats may alsobe used for passing information between the electronics package 205external display module 210. Along with data compression and encryption,data may be converted prior to being sent over the electrical connection250. For example, data representing the caliper's measurement may beconverted from into a digital signal or an analog signal (via ananalog-to-digital (A/D) converter or a digital-to-analog (A/D)converter) prior to transmission.

FIG. 3 a and FIG. 3 b illustrate an exemplary display 305 that presentsa decimal representation 310 of a measurement value simultaneously witha fractional representation 315. A units indicator 320 displays theunits of measure that are currently being displayed. The display 305also includes a variance indicator 330 that is capable of showing arelative indication of the approximate difference between the fractionalrepresentation 315 and the exact measurement. In the example of FIG. 3a, the exact measurement displayed on the decimal representation 310 is1.20 inches, however, the fractional representation 315 is set todisplay one-quarter inches as its finest resolution. As a result, thefractional representation 315 displays an approximation of the exactmeasurement; in this case, 1¼ inches. The variance indicator 330 in thisexample is embodied as a segmented bar, where the endpoints of the barrepresent the midpoints to the next unit of resolution (for example, theleft end would represent the displayed measurement minus ⅛ inch, and theright end would represent the measurement plus ⅛ inch), and the relativelocation of the exact measurement is represented by a highlightedsegment 335. Since the exact measurement is less than the approximatedfractional measurement 315, the variance indicator 330 is shown with thehighlighted segment 335 to the left (“smaller”) side of center.

FIG. 3 b illustrates the same display 305, except in this example theexact measurement is slightly greater than the approximated fractionalrepresentation 315. In this example, the exact measurement is 1.29inches but the current configuration for the fractional display 315causes the fractional display 315 to display the approximatedmeasurement as 1¼ inches. Since the exact measurement is greater thanthe approximated fractional measurement 315, the variance indicator 330is shown with the highlighted segment 335 to the right (“larger”) sideof center. If the exact measurement were 1.25 inches, then thehighlighted segment 335 would be shown in the center of the varianceindicator 330.

FIG. 3 c illustrates an exemplary display 350 that comprises a decimalrepresentation 355 of a measurement value simultaneously with afractional representation 360. The units indicator 365 displays units ofmeasure that are currently being displayed. In this example, variancebetween the exact measurement and the approximated fractionalrepresentation 360 is indicated by the left arrow 380 and a right arrow385, which point in the direction between the current location and theindicated approximate fractional representation 360. For example, in theillustration, the exact measurement is 1.20 inches, as indicated by thedecimal representation 355. However, the current configuration of thefractional representation 360 only allows for resolution of ¼ inch. Inthis case, the approximated fractional value displayed in the fractionalrepresentation 360 is larger than the exact decimal value displayed inthe decimal representation 355, so the right arrow 385 is highlighted toindicate the direction in which the measurement would have to move inorder to match the approximated fractional representation 360. In someother implementations, the arrows 380 and 385 may be highlighted in aninverse manner in order to indicate that the fractional representation's360 value is larger or smaller than the decimal representation's 355value.

FIG. 4 a, FIG. 4 b, and FIG. 4 c illustrate displays that implementmultiple discrete display elements. FIG. 4 a illustrates an exemplarydisplay 405 that is capable of displaying both a decimal and factionalrepresentations of a measurement. In particular, the display 405includes a decimal display 410 and a fractional display 412. The decimaldisplay 410 includes a decimal representation 414 of the presentmeasurement and a units indicator 416. The fractional display 412includes a fractional representation 418 and a units indicator 420.

FIG. 4 b illustrates an exemplary display 440 that includes two discretedisplays, a first decimal display 442 and a second decimal display 444,which are capable of displaying a single measurement using two differentmeasurement units. As illustrated, the first decimal display isconfigured to display measurements and units of inches, and the seconddisplay is configured to display measurements in units of millimeters.The first display 442 includes a first decimal display 446 and a unitsindicator 448. In this example the first units indicator 448 representsthe measurement units as “inches” in an abbreviated form (“In”). Thesecond display 444 includes a second a small display 450 and a secondunits indicator 452. In this example the second units indicator 452represents the measurement units as “millimeters” in an abbreviated form(“mm”). In various embodiments, the display 440 may be capable ofdisplaying other units of measurement such as microns, meters, feet,centimeters, and other well known or user defined units.

FIG. 4 c illustrates an exemplary display 470 with two discretedisplays, a decimal display 472 and a fractional display 474. Thedecimal display 472 includes a decimal representation 476 in a unitsindicator 478 that are similar to previously described displays. Thefractional display 474 includes a fractional indicator 480 and a unitsindicator 482. In this example, the fractional indicator 480 implementsan alternative technique for representing fractional values. In someembodiments, the fractional display 474 may be implemented using aseven-segment display. As known in the art, seven segment displaystypically are not capable of displaying a “slash” (e.g. “/”) between thenumerator and denominator (e.g., ½, ⅓, ¼) as would be required in orderto display a fractional value using traditional notation. In order todisplay fractional representations of numbers, an alternative method fordisplaying the “slash” may be implemented. As an example of fractionalrepresentation 480, the “slash” may be represented by a horizontal line485 or “dash” (e.g., “-”) of which typical seven-segment displays arecapable of displaying. In this example, the fractional number “1¼” couldbe represented on a seven-segment display as “1 1-4”. And someembodiments, the “slash” could be represented by decimal point (e.g.,“.”) which most seven-segment displays are also capable of displaying.In such an implementation the fractional number “1¼” be represented on aseven-segment display as “1 1.4”.

FIG. 5 Illustrates a flow chart 500 that represents some operations ofthe display 185. The display driver 185 may be executed individually oras a portion of a portion of a software process or module. In someimplementations, execution of the display driver 185 may be initiated byan input (e.g., the user pressing a button) or may execute continuouslyupon power-up of the electronic package, or other type of event. In someimplementations, the execution may be repeated for each availabledisplay (e.g., display 410 and display 412 shown in FIG. 4A). In thisexample, that the target display has been selected prior to theexecution. At step 502, the display driver 185 reads presentationsettings that control the display and format of measurement information(e.g. measurement units, decimal or fractional representation, etc.).These presentations settings may be gathered from inputs, from settingsstored in memory (e.g., memory 180), configuration switches, etc.

At step 504, measurement data is acquired from the caliper's measurementhardware (e.g., encoders, transducers, etc.). In this example, themeasurement data is given in an internal representation (e.g., a binaryrepresentation) that may not be directly useful to the user because itis not given in any standard unit of measurement. In step 506, thisinternal representation is converted to measurement units (e.g., inches,mm, etc.), according to the presentation settings read in step 502.Furthermore, one or more data format metrics may be selected. Forexample, the precision of the presented data may be selected (e.g.,quarter inch precision, eighth inch precision, tenth of a centimeterprecision, etc.) by a user or predefined. In some implementations,operations of the display driver 185 may include rule engine operationsto apply the selected precision or one or more other data formatmetrics. For example, if a quarter inch precision is selected; and thecaliper measures 7/16 of an inch; a numerical value of ½ of an inch maybe assigned to represent the measurement.

At step 508, if the presentation settings call for the measurement to beformatted as a decimal value, the process continues at step 510. If thepresentation settings call for the measurement to be formatted as afractional value, the process continues at step 512. At step 510, theunits measurement is formatted as a decimal value. At step 512, theunits measurement is formatted as a fractional value. In someimplementations, to simultaneously present representations on twodisplays (e.g., a decimal representation and a fractionalrepresentation), steps 510 and 512 are sequentially executed in tworepetitive passes through the flow chart 500. In other implementations,steps 510 and 512 may be executed together for simultaneous presentationtwo displays (rather than in a repetitive manner for each display). Forexample a dedicated processor or processing engine may be assigned toeach display and independently execute the operations of flow chart 500.Processing sharing and multitasking techniques may also be implementedfor simultaneous displaying of the representations.

At step 514, the formatted measurement is presented to the display. Thisstep may include sending raw characters to a display, sending drawingcommands that represent the value to be displayed, etc. In someimplementations, the operations of the display driver 185 may passcontrol back to another process, or one or more operations may bere-executed in a repetitive manner, or other operations may be executed.

FIG. 6 illustrates a flow chart 600 of exemplary operations executed bythe display driver 185 for displaying a fractional value with a varianceindicator (such as variance indicator 330, or arrows 380 and 385). Thedisplay driver 185 may be executed independently or in combination withone or more other software processes or modules. In someimplementations, execution of the display driver 185 may be initiated byan input (e.g., the user pressing a button) or may execute continuouslyupon power-up of the electronic package, or other type of event. In someimplementations, the execution may be repeated for each availabledisplay (e.g., two displays). In this example, the target display hasbeen selected prior to the process starting. However, in someimplementations multiple displays may be selected. For example,operations associated with two or more instances of the display driver185 may be executed by one or more processors or other types ofprocessing engines.

At step 602, the process receives input data that includes data thatrepresents the current position of the caliper (i.e. a measurement). Inthis example, the measurement data is given in an internalrepresentation that may not be useful to the user (e.g., because it isnot in any standard unit of measure). The input data may also compriseinformation concerning display selection, measurement units, fractionalresolution, precision, etc.

At step 604, operations of the display driver 185 include selecting anindividual display based upon information contained in the input data.At step 606, the display driver 185 selects the measurement units forthe display based upon information also contained in the input data. Insome implementations, this step may also include the process ofconverting measurement data from the internal representation to “realworld” units (e.g., inches, mm, etc.).

At step 608 if input data indicates that a decimal format has beenselected, then the process continues at step 610. At step 610, theprocess shows the decimal measurement on the selected display. In someimplementations once this step has been completed, control may returnback to the calling process. In some implementations, the process mayreturn to step 602.

At step 608, if the input data indicates that the fractional format hasbeen selected, then the process continues at step 612. At step 612, theprocess shows the fractional measurement on the selected display.

At step 614, the process determines whether the exact measurement valueis greater than or less than the fractional value. If the exactmeasurement value is not greater than or less than the fractional value,the process returns to step 602, for example. In some implementations,such as those that have a variance indicator similar to that asillustrated by the variance indicator 330, this step may also includeplacing the highlighted segment 335 in a centered position.

If at step 614 the process determines that the exact measurement valueis greater than or less than the fractional value, then the processcontinues at step 616. At step 616, the process shows the varianceindication on the selected display after which may return to step 602.

In various implementations, the manner in which fractional resolution isdetermined may be implemented in various ways. For example, the minimumfractional resolution may be permanently set in the caliper according tofractional resolution that is found in common hand tools, such as 1/32inch and 1/64 inch. In another example, the minimum fractionalresolution may be configured by the user, which may be useful if theuser knows that the objects being measured only fall within a knownmeasurement resolution range (e.g., ¼ inch resolution for parts thatmeasure ¼ inch, ½ inch, ¾ inch, etc., but are never ⅛ inch, ⅜ inch, 3/16inch, etc.). The user may not be concerned with seeing measurements thatcorrespond to common tool sizes, and may therefore wish to set thefractional resolution to value not commonly seen in hand tools (e.g.,1/128 inch, 1/20 inch, etc.).

There may be instances where the user may wish to represent fractionalvalues in nonstandard formats. In some implementations, the caliper maybe configured to allow for a fixed denominator value. For example, whenmeasuring by ¼ inch increments, a fraction is usually simplified to anequivalent fraction in lowest terms (e.g. 0, ¼, ½, ¾, 1 . . . ). A usermay configure the caliper to show fractions with a fixed denominator someasurements may not appear in lowest terms (e.g., 0/4, ¼, 2/4, ¾ 4/4 .. . ). In some embodiments, the caliper may also be configured todisplay fractional measurements using improper fractions (e.g., 5/4,22/16, etc.).

In some embodiments, the caliper may also include an output for drivingan external video display, such as a video monitor, television, headmounted display, etc. This output may be in the form of an analog videosignal (e.g., modulated RF, composite video, super video, componentvideo, VGA, etc.) and/or a digital video signal (e.g., IEEE1394, DVI-D,HDMI, etc.). In some embodiments, this external video display may takethe place of any internal or attached display device previouslydescribed.

In some embodiments one or more processors, such as processor 175, mayexecute instructions to perform the operations of the caliper 100 or thecaliper 200, e.g., respectively represented in flowchart 500 and 600.For example, one or more general processors (e.g., a microprocessor)and/or one or more specialized devices (e.g., an application specificintegrated circuit (ASIC), etc.) may execute instructions. One or moreof the processors may be implemented in a single integrated circuit as amonolithic structure or in a distributed structure. In some embodimentsthe instructions that are executed by the processors may reside in amemory (e.g., random access memory (RAM), read-only memory (ROM), staticRAM (SRAM), etc.), such as memory 180. The instructions may also bestored on one or more mass storage devices (e.g., magnetic,magneto-optical disks, or optical disks, etc.).

One or more of the operations associated with the caliper 100 or thecaliper 200 may be performed by one or more programmable processors(e.g., a microprocessor, an ASCI, etc.) executing a computer program.The execution of one or more computer programs may include operating oninput data (e.g., data provided from a source, etc.) and generatingoutput (e.g., sending data to a destination, etc.). The operations mayalso be performed by a processor implemented as special purpose logiccircuitry (e.g., an FPGA (field programmable gate array), an ASIC(application-specific integrated circuit), etc.). Processors and memorycan be supplemented by, or incorporated in special purpose logiccircuitry.

Operation execution may also be executed by digital electroniccircuitry, or in computer hardware, firmware, software, or incombinations of them. The operations described in flowcharts 500 and 600(as well as the Display Driver 185) may be implemented as a computerprogram product, e.g., a computer program tangibly embodied in aninformation carrier, e.g., in a machine-readable storage device (e.g.,RAM, ROM, hard-drive, CD-ROM, etc.) or in a propagated signal. Thecomputer program product may be executed by or control the operation of,data processing apparatus, e.g., a programmable processor, a computer,or multiple computers. A computer program may be written in one or moreforms of programming languages, including compiled or interpretedlanguages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, or other unitsuitable for use in a computing environment. A computer program may bedeployed to be executed on one computing device (e.g., controller,computer system, etc.) or on multiple computing devices (e.g., multiplecontrollers) at one site or distributed across multiple sites andinterconnected by a communication network.

One or more types of content presentation technologies may be used toimplement the dual displays (such as display 126). For example, displaydevices that use light emitting diode (LED), a cathode ray tube (CRT),liquid crystal display (LCD), monitor, or other technologies may beimplemented individually or in combination.

1. An apparatus comprising: a caliper configured to measure at least onephysical dimension; a display configured to present a firstrepresentation and a second representation of a measurement provided bythe caliper, wherein a format of the first representation is differentfrom a format of the second representation, and the first representationis approximately simultaneously displayed with the secondrepresentation, and wherein the display is configured to present arepresentation of an approximate difference between the firstrepresentation and the second representation of the measurement.
 2. Theapparatus of claim 1, wherein the format of the first representationincludes one of a decimal format and a fractional format.
 3. Theapparatus of claim 2, wherein the format of the second representationincludes one of a decimal format and a fractional format, and isdifferent from the format of the first representation.
 4. The apparatusof claim 1, wherein the format of the first representation has metricunits and the format of the second representation has U.S. units.
 5. Theapparatus of claim 1, wherein the resolution of the first representationis selectable.
 6. The apparatus of claim 1, wherein the format of thefirst representation includes a first measurement unit and the format ofthe second representation includes a second measurement unit, differentfrom the first measurement unit.
 7. The apparatus of claim 1, furthercomprising: an electronics package that includes the display.
 8. Theapparatus of claim 1, wherein the display includes a unit indicator. 9.The apparatus of claim 1, wherein the display includes a varianceindicator.
 10. The apparatus of claim 1, further comprising: anelectronics package configured to provide data representative of thefirst representation and the second representation to an externaldisplay module.
 11. The apparatus of claim 10, wherein a hardwireconnection provides the data from the electronics package to theexternal display module.
 12. The apparatus of claim 10, wherein awireless connection provides the data from the electronics package tothe external display module.
 13. A method comprising: simultaneouslydisplaying on a display of a caliper, a first representation and asecond representation of a measurement provided by the caliper, whereina format of the first representation is different from a format of thesecond representation, and displaying a representation of an approximatedifference between the first representation and the secondrepresentation of the measurement.
 14. The method of claim 13, furthercomprising: providing data that represents the first representation andthe second representation to an external display module.
 15. The methodof claim 13, wherein the format of the first representation includes oneof a decimal format and a fractional format.
 16. The method of claim 13,wherein the format of the first representation has metric units and theof the second representation format has U.S. units.
 17. A computerprogram product, encoded on a computer-readable medium, operable tocause a data processing apparatus to perform operations comprising:simultaneously displaying on a display of a caliper, a firstrepresentation and a second representation of a measurement provided bythe caliper, wherein a format of the first representation is differentfrom the format of the second representation, and displaying arepresentation of an approximate difference between the firstrepresentation and the second representation of the measurement.
 18. Thecomputer program product of claim 17, further operable to cause the dataprocessing apparatus to perform operations comprising: providing datathat represents the first representation and the second representationto an external display module.
 19. The computer program product of claim17, wherein the format of the first representation includes one of adecimal format and a fractional format.
 20. The computer program productof claim 17, wherein the format of the first representation has metricunits and the of the second representation format has U.S. units.